An important missing source of atmospheric carbonyl sulfide: Domestic coal combustion

Carbonyl sulfide (COS), carbon monoxide (CO), and sulfur dioxide (SO2) emissions generated from prevailing domestic coal stoves fueled with raw bituminous coal were studied under alternation cycles of flaming and smoldering combustion. The measurements in the laboratory and the farmer's house indicated that COS and CO emissions mainly occurred under the condition of flame extinguishment after coal loading, whereas SO2 emissions were mainly generated through combustion with flame. The COS emission factors for the domestic stoves in the laboratory and the farmer's house were recorded as 0.57 ± 0.10 g COS kg−1 and 1.43 ± 0.32 g COS kg−1, being approximately a factor of 50 and 125 greater than that generated from coal power plants, respectively. Based on the COS emission factors measured in this study, COS emission from only domestic coal combustion in China would be at least 30.5 ± 5.6 Gg S yr−1 which was 1 magnitude greater than the current COS estimation from the total coal combustion in China. Key Points COS emissions from domestic coal combustion are mainly ascribed to coal loading and smoldering combustion COS emission factor from domestic coal combustion was found to be approximately a factor of 50 greater than that from power plants Current global emissions of COS from coal combustion must be substantially underestimated